DBS are currently supporting North Tyneside Council with their duties under Part 2A of the Environmental Protection Act 1990. Part 2A infers statutory obligations on Local Authorities to deal with contaminated land within their borough. DBS are supporting the council on the long term management of a historical landfill site in North Tyneside.
Like most areas of the UK, there is a historical legacy of landfill sites in the North East that were infilled prior to the Control of Pollution Act 1974 (often referred to as COPA 1974). Prior to COPA 1974, domestic and industrial wastes were deposited anywhere where there was a big enough hole in the local area, and there was no requirement on the waste managers to keep records, or, to implement landfill engineering methods to contain pollution from the wastes.
Landfills produce leachate as a result of moisture in the waste being squeezed out due the volume of the waste mass, from groundwater present within the base of a site (e.g in a valley or quarry feature), and from infiltration reaching waste deposits from rain. Leachate can contain a range of organic and inorganic contaminants, and also, as waste breaks down under anaerobic and aerobic conditions, bacteria within the deposits feed on the waste mass and generate gas as a waste product. The gas produced typically comprises methane and carbon dioxide in a 60:40 ratio, along with other trace gases.
As a result, it is important that landfill sites are properly monitored and managed to prevent negative impacts arising due to problems such as uncontrolled gas migration. Methane is explosive in air in the range 5% to 15% by volume, and carbon dioxide is an asphyxiant as it replaces oxygen in the respiratory tract in humans.
DBS have been monitoring the landfill site on behalf of the council to confirm that lateral gas migration is not occurring, and we have also implemented engineering work including the remediation of an existing granular gas vent trench to mitigate potential for gas movement outside of the landfill, and repair and replacement of existing gas and groundwater monitoring wells. This work is assisting in the long term management of the site.
DBS have also undertaken an intrusive investigation of shallow soils in the vicinity of the landfill site to determine the contamination status of the superficial deposits, and we are currently preparing an interpretative report for the council on this work, the report includes detailed contaminated land risk assessments for human health and property, and provides an updated Conceptual Site Model. The report also includes a detailed ground gas risk assessment based on historical and current landfill gas monitoring data, this work has identified that significant risks from landfill gas to the surrounding area are not present.
The work undertaken by DBS is allowing the council to target resources for future management of the landfill site under Part 2A, and to ensure that any potential risks to public health are properly understood, monitored and controlled.
Some photos of the vent trench remediation, borehole headwork’s repair, cable percussion drilling for new perimeter monitoring wells and window sampling for contamination off site are provided below.